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The identification of liquid ethane in Titan’s Ontario Lacus

Abstract

Titan was once thought to have global oceans of light hydrocarbons on its surface1,2,3,4,5, but after 40 close flybys of Titan by the Cassini spacecraft, it has become clear that no such oceans exist6. There are, however, features similar to terrestrial lakes and seas7, and widespread evidence for fluvial erosion8,9, presumably driven by precipitation of liquid methane from Titan’s dense, nitrogen-dominated atmosphere10. Here we report infrared spectroscopic data, obtained by the Visual and Infrared Mapping Spectrometer11 (VIMS) on board the Cassini spacecraft, that strongly indicate that ethane, probably in liquid solution with methane, nitrogen and other low-molecular-mass hydrocarbons, is contained within Titan’s Ontario Lacus.

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Figure 1: VIMS and radar images of the lake at 78° N, 250° W, and ISS and VIMS images of Ontario Lacus.
Figure 2: Spectra of regions in and around Ontario Lacus.
Figure 3: Plot of 5-μm brightness against airmass for the lake interior and an adjacent region outside of Ontario Lacus.
Figure 4: Ratio spectrum of Ontario’s interior, with a model spectrum of liquid ethane superimposed.
Figure 5: Model spectrum of liquid ethane simulating the effects of aerosol scattering and atmospheric opacity.

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Brown, R., Soderblom, L., Soderblom, J. et al. The identification of liquid ethane in Titan’s Ontario Lacus. Nature 454, 607–610 (2008). https://doi.org/10.1038/nature07100

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